问preg_match必须以"/“结尾？

EN

  $url = get_bloginfo('url')
//$url = 'http://site.com'

  $my_folder = get_option('my_folder');
//$my_folder = 'http://site.com/somefolder;

 http://somefolder/go/

 http://somefolder/go

 http://somefolder/gone

$my_folder =  get_option('rseo_nofollow_folder');
if($my_folder !=='') $my_folder = trim($my_folder,'/');
$url = trim(get_bloginfo('url'),'/');

preg_match_all('~<a.*>~isU',$content["post_content"],$matches);

for ( $i = 0; $i <= sizeof($matches[0]); $i++){
    if($my_folder !=='')
    {
    //HERES WHERE IM HAVING PROBLEMS

        if ( !preg_match( '~nofollow~is',$matches[0][$i]) 
            && (preg_match('~' . $my_folder . '/?$~', $matches[0][$i]) 
            || !preg_match( '~'. $url .'/?$~',$matches[0][$i])))
        {
            $result = trim($matches[0][$i],">");
            $result .= ' rel="nofollow">';
            $content["post_content"] = str_replace($matches[0][$i], $result, $content["post_content"]);
        }
    }
    else
    {
    //THIS WORKS FINE, NO PROBLEMS HERE
        if ( !preg_match( '~nofollow~is',$matches[0][$i]) && (!preg_match( '~'.$url.'~',$matches[0][$i]))) 
            {
            $result = trim($matches[0][$i],">");
            $result .= ' rel="nofollow">';
            $content["post_content"] = str_replace($matches[0][$i], $result, $content["post_content"]);
            }
    }
}
return $content;